Okay, after hearing about the fact we have a Batman now (Affleck), I've been inspired to write a possible teaser trailer, with heavy nods to Jeph Loeb (hey, he helped inspire the Dark Knight trilogy and some of the Kansas scenes of Man of Steel, so why not this film?) and a bit to Dini/Timm:

We begin with LIGHTNESS, BRILLIANT WHITE. But then we hear a voice, a voice of THE MAN OF STEEL, SUPERMAN. We hear strains of Zimmer's MOS score.

SUPERMAN (v.o.)
The dream always begins the same...

RAPID CUT of stock footage of Jor-El and Lara, Krypton, the launch of Kal-El's ship, it going by the moon, the destruction of Krypton etc. from MOS, as Superman continues to voice-over it

SUPERMAN (v.o)
...My parents, sending me into space as their world died around them. Hope surviving in me...

Abrupt cut to utter blackness, the music stops, and as Zimmer's (presumably) new theme for BATMAN begins (a bit more heroic sounding than the Dark Knight themes, but still noticably dark and gritty), we hear the voice of THE BATMAN.

BATMAN (v.o)
The nightmare always begins the same....

Abrupt cut to footage of Batman's origin- perhaps it's specifically shot for the teaser, perhaps it is from a brief one-or-two minute "if you are one of the four people who don't know Batman's origin, here's the deal" sequence from the film- either way, we see some of those images: of a family leaving a theater, of a mugger, of a gunshot and pearls falling to the ground and a child wailing and then a Bat screeching, and through it all, Batman continues his voiceover:

BATMAN (v.o)
...My parents, dead at the hands of a gunman from the shadows. My childhood dying, a WAR beginning...

Now we cut to the light and the dark next to each other, as images and footage of the two heroes- both from the film, MOS and some select comics, play briefly as now the music weaves together and the two heroes speak alongside each other

SUPERMAN (v.o.) / BATMAN (v.o)
I was born with powers beyond those of other men... / I have honed my mind and body to be better than other men...

Slowly, the LOGOs of the two heroes begin to emerge, as the dual speech continues...

SUPERMAN (v.o) / BATMAN (v.o)
I need to use them to be a champion, an inspiration to the people of Earth... / I have become a legend, a myth, a bogeyman to the criminals of Gotham...

The LOGOS are now fully on the screen, separated by the line between light and darkness.

The LOGOS COLLIDE, light and darkness merge and fracture alongside each other, the logo of the film now stands there, as the two heroes finish their speeches and the music crescendos:

SUPERMAN (v.o) / BATMAN (v.o)
I'm Superman! / I am Batman!

CUT TO the release date of July 17, 2015, and then, before the standard showing of credits that they show at the end of trailers, we get a quick 2 second look at the two heroes looking at each other, meeting face to face for the first time.... and then credits... and then... BLACK.